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Europaisches Patentamt
European Patent Office
Office europeen des brevets

0 569 489 B1

EUROPEAN PATENT SPECIFICATION

G05B 13/00

so A SYSTEM FOR RESISTING LIMB MOVEMENT.

CD
00

CD
LO

@ Date of publication of application:
18.11.93 Bulletin 93/46

Designated Contracting States:

AT BE CH DE DK ES FR GB GR IT LI LU MC

NL SE

WO-A-85/04796
FR-A- 2 624 002
US-A- 4 760 850

77 Massachusetts Avenue
Cambridge, MA 02139 (US)

Representative: Greenwood, John David et al

Graham Watt & Co.

Riverhead

Sevenoaks

Kent TN13 2BN (GB)

Note: Within nine months from the publication of the mention of the grant of the European patent, any person
may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition
shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee
has been paid (Art. 99(1 ) European patent convention).

Rank Xerox (UK) Business Services

(3. 10/3.09/3.3.3)

EP 0 569 489 B1

Description

Background Art

Orthoses, or limb assistive devices, have been
developed to assist disabled persons in performing
daily functions. One application for such devices is
in stabilizing limb motion in tremor patients.

The presence of random involuntary limb
movement superimposed on purposeful limb move-
ment is an abnormal condition that afflicts hun-
dreds of thousands of patients suffering from a
variety of diseases. Many tremor patients are dis-
abled by these involuntary movements due to the
fact that the amplitude of these movements is large
enough to degrade or obscure voluntary movement
attempted by the patient. Cerebral palsy patients
suffering from athetosis may also be disabled by
their involuntary limb movement. Chorea is another
such condition.

In each of these cases, patients typically try to
overcome the disability imposed by the involuntary
movements of a particular limb, either by steadying
the motion using an unafflicted limb, by jamming
the afflicted limb against the body so as to restrict
its vibration, or even by having another person
grasp the limb to steady its motion. Drug therapies
and surgery have been attempted with limited ef-
fectiveness and considerable risk for the patient.

However, in the past ten years or so, a number
of orthoses have been developed for selectively
suppressing random involuntary movements. These
devices are based on the observation that signifi-
cant reduction of the involuntary movements can
be achieved by the application of viscous damping
to the afflicted limb or body segment.

One such device is a one degree-of-freedom
(DOF) orthosis with an electronically-controlled
magnetic particle brake used to retard limb motion
(See Dunfee, D.E., "Suppression of IntentionTrem-
or by Mechanical Loading", M.S. thesis, M.l.T. De-
partment of Mechanical Engineering, February
1979). This device, meant primarily for conducting
experiments on the wrist, prevents the patient from
performing whole-arm functional activities, since
limb motion is rigidly constrained in the remainig
DOF's.

Another prior art device is a 2 degree-of-free-
dom joystick used as a control interface to elec-
trical devices (such as powered wheelchairs) while
applying a resistive load to the limb. This system
also cannot be used for whole-arm movements and
is not meant as a general purpose functional or-
thosis. A third prior art device is a two degree-of-
freedom arm and hand brace that controls involun-
tary neuro-muscular spasms and permits the per-
formance of controlled arm and hand movements
(see U.S. patent No. 4,237,873). The system de-

scribed in this patent comprises a plurality of links
joined by joints to form a linkage system between
a fixed point in space and a movable end point of
said linkage system, a limb coupler for coupling a

5 limb to said end point, and means for resisting
rotational link movement about two mutually or-
thogonal axes.

Despite such work, a need exists for an or-
thosis which will enable full-arm movement, which

10 requires six degrees of freedom in a safe and
reliable manner. Such a device would be useful not
only for tremor suppression, but would also find
application in physical therapy and exercise ma-
chines, especially if the device were capable of

15 achieving force-velocity colinearity. Force-velocity
colinearity occurs when a force is applied to a
device endpoint and the device moves in the direc-
tion of the force; resulting in a natural cause and
effect result.

Summary of the Invention

The invention consists of a system for resisting
the motion of a subject's limb about six DOF's, and

25 comprises a passive manipulator that can be used
in conjunction with a microcomputer, a display
monitor and electronic circuitry to process manipu-
lator outputs for use by the microcomputer. The
manipulator comprises a plurality of links, joined

30 together by revolute joints to form a linkage system
between a fixed point in space and a movable
endpoint of the linkage. As the endpoint of the
linkage is moved by the subject's limb, the joints of
the linkage -- and hence, the links themselves

35 --rotate.

The rotation of certain joints in the linkage are
resisted by a plurality of brakes (such as particle
brakes). These joints allow translational motion of
the endpoint in three DOF's and rotational motion

40 of the endpoint about each of three mutually or-
thogonal axes. The limb (an arm) is coupled to the
manipulator endpoint by a limb coupling cuff, the
motion of the limb is resisted in six DOF's (three
translational, three rotational).

45 The manipulator endpoint force acting to resist

the arm motion is in a direction opposite the end-
point velocity vector, resulting in substantial force-
velocity colinearity (FVC). FVC is attained when the
force the human arm imparts is in the same direc-

50 tion as the desired movement.

Brief Description of the Drawings

Figure 1 is a block diagram of an example
55 therapeutic system in which the manipulator of the
invention may be used.

Figure 2 is a block diagram of the manipulator
of the invention.

EP 0 569 489 B1

Figure 3 depicts the links, joints, force-torque
sensor, limb coupling cuff and counterbalance
weights comprising the manipulator linkage.

Figure 4 is a dynamic equivalent of the ma-
nipulator linkage shown in Figure 3.

Figure 5 is a schematic of a magnetic particle
brake.

Figure 6 is a schematic of the transmission for
joint 300 of Figure 3, depicting links, a particle
brake, a reducer and a potentiometer.

Figure 7 is a schematic of the transmission for
joints 308 and 314 of Figure 3, depicting links,
particle brakes, reducers and potentiometers.

Figure 8 is a schematic of the voltage divider
circuit equipped with a potentiometer to measure
position.

Figure 9 illustrates the moving target and Ma-
nipulator crosshair that appear on the display moni-
tor in the pursuit tracking task.

Figures 10a and 10b are the top view and
cross-sectional views, respectively, of the elastic
element and strain gauges of the force-torque sen-
sor.

Figures 11a and 11b are the top and side
views of the strain gauges on a single spoke of the
elastic element.

Figures 12a and 12b are schematics of the
Wheatstone bridge circuits for the horizontal and
vertical components of the applied load.

Detailed Description of the Invention

A preferred embodiment of the invention will
now be described in connection with Figure 1 . This
embodiment illustrates a six DOF device coupled
to an arm of a subject. However, it is to be under-
stood that the invention is not limited thereto and
may in fact have greater or fewer DOF's and may
be useful for coupling to other limbs. Also, it should
be noted that while the term "manipulator" is used
for convenience, the system is passive and the
subject does the "manipulating". The system only
restrains or resists forces exerted by the subject's
limb. The manipulator 100 of the invention is one
component in a physical therapeutic system com-
prised of (1) the manipulator 100; (2) a human
subject 102; (3) a microcomputer 104 primarily
used to process data and adjust resistive forces
within the manipulator; (4) electronics 106 to
preprocess data from the manipulator destined for
the computer; and (5) a computer monitor 108 to
display a moving object.

The manipulator 100 is shown in the block
diagram of Figure 2 wherein mechanical connec-
tions are shown in dotted/dashed lines and elec-
tronic connections in solid. A linkage set 200, is
mechanically coupled to brakes 202 which restrain
the motion of certain joints in the linkage 200.

Reducers 204 amplify the torques produced by the
brakes 202. Position and velocity sensors 206 mea-
sure the angles about which certain joints have
been rotated and the angular velocities, respec-

5 tively. A force-torque sensor 208 yields measure-
ments of loads applied at the manipulator endpoint.
Counterbalances 210 compensate load imbalances
about certain joints and a limb coupling cuff 212
couples the arm 102a to the manipulator endpoint.

w Each of these components will now be described in
detail in the following sections:

I. Linkage

is The manipulator linkage 200 of Figure 3 com-

prises a set of 15 aluminum tubes or 'links' 338-
366 joined together by 18 revolute joints 300-334
that allow rotation of the links with respect to one
another. In the figure, the butterfly-shapes (x)

20 300-306 represent one of four joints having rotation
axes lying in the plane of the paper, while circles
(O) 308-334 denote one of fourteen joints having
rotation axes normal to the plane of the paper.

The composite linkage structure 200 permits

25 motion in six DOF's. The 6 DOF motion is more
clearly seen in the simplified dynamic equivalent of
Figure 3, shown in the manipulator linkage drawing
of Figure 4. In Figure 4, the rotation of joint 300
about its axis produces rotation in the ±<j> directions

30 of a standard spherical coordinate system centered
at joint 308. Joints 308 and 402 are coupled by a
trapezoidal linkage T (shown in Figure 3, but not in
Figure 4). Rotation of the coupled structure 308,
402, T about joint 308 causes rotation of the ma-

35 nipulator linkage in the ±6 directions, and a com-
bination of rotations of joints 308 and 402 causes
translational movement in approximately the ±r di-
rections. Hence, joints 300, 308 and 402 are re-
sponsible for positioning the manipulator endpoint

40 in three dimensional space. Note that the manipula-
tor endpoint E, defined as being the point at which
the manipulator linkage 200 is coupled to the limb
of the subject 102, roughly corresponds to the
distal end of link 408 of Figure 4.

45 Joints 404, 406 and 306 are used to change

the orientation of the manipulator endpoint E. Rota-
tion about the axis of the joints 404, 406, 306
corresponds to rotation about each of three mutu-
ally orthogonal axes of a coordinate system cen-

50 tered at joint 406. In other words, rotation of joint
404 produces roll motion at the endpoint, rotation
of joint 406 produces pitch motion at the endpoint,
and rotation of joint 306 produces yaw motion at
the endpoint.

55 The more complicated structure of Figure 3 is

the linkage structure that is preferred in the present
embodiment because of several practical limita-
tions that arise in the simpler six-joint structure of

EP 0 569 489 B1

Figure 4. For example, it is difficult to obtain a
rotationaliy-stiff system with the simpler design.
Size and weight limitations are also present, and
the system of Figure 4 would suffer from backlash
and chordal speed variation.

To overcome these limitations, a number of
auxiliary joints 302, 310, 312, 316-332 that are not
present in the Figure 3 structure are introduced in
the Figure 4 structure. While joints 300, 306 and
308 of Figure 4 correspond to single joints des-
ignated by the same reference numbers as in
Figure 3, joints 402, 404 and 406 of Figure 4 are
implemented by sets of joints in Figure 3. Specifi-
cally, joint 402 corresponds to a coupling of joints
308-314, joint 404 corresponds to the pair of joints
302 and 304 and joint 406 corresponds to the set
of joints 316-334.

Referring back to Figure 3, link 336 is used to
couple the entire manipulator structure (and in par-
ticular, joint 300) to a fixed external surface, such
as a floor. Link 338 couples joints 300 and 308
together. Joint 308 is part of a trapezoidal four-bar
linkage T comprising the four links 342-348 with
joints at the vertices (i.e., connecting pairs of adja-
cent links in the trapezoid). Namely, joints 308 and
314 connect link pairs 342, 344 and 344, 348
respectively, while joints 310 and 312 connect pairs
342, 346 and 346, 348 respectively. As the four
joints 308-314 rotate together appropriately, the
shape of the trapezoid is changed, thereby causing
the manipulator endpoint E to travel in approxi-
mately the ±r direction of a spherical coordinate
system centered at joint 308 (i.e., along the dotted
line 368). The current ±r direction is determined by
the values of the azimuth and elevation angles <i>
and 6 as determined by the amounts that joints 300
and 308 have been rotated.

The remaining links and joints of the manipula-
tor of Figure 3 constitute a novel gimbal link geom-
etry referred to as the 'upper linkage, 1 which pro-
vides the three orientational DOF's corresponding
to joints 404, 406 and 306 of Figure 4. The upper
linkage comprises three parallelograms Pi , P 2 , P3
of links and joints. In the central parallelogram Pi ,
joints 302 and 304 are coupled to either end of the
trapezoidal linkage's link 348, with both joints pro-
viding a roll motion for the upper linkage. Attached
to the other side of joint 302 is link 350, which joins
with link 360 at joint 322. Attached to the other side
of joint 304 is link 366, which meets link 354 at
joint 326. The fourth side of the central parallel-
ogram Pi consists of link 352, which is attached to
link 360 at joint 324 and to link 354 at joint 328.

The left parallelogram P2 consists of links 350,
360, 362 and 364 and joints connecting adjacent
pairs of these links. Specifically, pairs of links 350
and 362, 362 and 364, 364 and 360, and 360 and
350 are joined by joints 320, 316, 318 and 322,

respectively. Note that links 350 and 360 of the left
parallelogram P2 are merely extensions of the
same links of the central parallelogram Pi . Finally,
the upper right vertex of the left parallelogram is

5 coupled to the lower left vertex of the central
parallelogram Pi at joint 322.

The right parallelogram P 3 has as its sides
links 352, 354, 356, and 358 and joints connecting
adjacent pairs of these links. Specifically, pairs of

10 links 352 and 354, 354 and 356, 356 and 358, and
358 and 352 are joined by joints 328, 330, 332 and
334, respectively. Note that links 352 and 354 of
the right parallelogram P3 are merely extensions of
the same links of the central parallelogram Pi .

15 Finally, the lower left vertex of the right parallel-
ogram P3 is coupled to the upper right vertex of
the central parallelogram Pi at joint 328.

The upper linkage in Figure 3 simulates the
function of joint 406 in Figure 4 in that it produces

20 a pitch motion in which the effective rotation is
about a rotation axis 370 (point E) located at the
intersection of links 366 and 372 if they were to be
extended, and normal to the plane of the paper.
The pitch motion is accomplished by deforming the

25 parallelograms Pi , P2, P3 from rectangles to non-
rectangles, with the deformation taking place as the
joints 316-334 rotate in unison.

Finally, link 358 extends past joint 334 and
couples with joint 306, which is responsible for

30 producing a yaw motion. The other side of joint
306 is connected to link 372, which consists of the
force-torque sensor 374 attached to the limb cou-
pling cuff 376 worn by the subject.

35 II. Controlled Brakes

Six joints of the manipulator are coupled to
controlled braking devices that resist manipulator
endpoint motions imparted by the user in each of

40 the six DOF's. The brakes for the DOF's cor-
responding to joints 300, 308 and 306 are labelled
B1, B2 and B3, respectively, of Figure 3 and are
located near, and coupled to, the joints of Figure 3
bearing the same reference numerals, while the

45 brakes B4, B5, B6 for the DOF's corresponding to
joints 306, 404 and 406 of Figure 4 are located
near joints 306, 302 and 316 of Figure 3, respec-
tively. The last three brakes are not near their
respective joints but are instead located at other

50 joints primarily because the alternate joint locations
are better suited to provide counterbalancing (see
Section VII).

A variety of braking mechanisms may be used
to retard joint motion. These include electric mo-
55 tors, hydraulic actuators, mylar brakes, and mag-
netic particle brakes. In the present embodiment,
magnetic particle brakes are used. The choice was
motivated by the simplicity, reliability, low cost, and

EP 0 569 489 B1

ease of computer control associated with such
brakes.

A typical magnetic particle brake B1 is shown
in Figure 5, to consists of a disk 500 that is
attached to an output shaft 502. Note that in joints
lacking reducers, the axis A of the output shaft 502
is the rotational axis of the joint (as will be seen in
Section III). The disk 500 resides in a cylindrical
cavity 504 larger than the disk. Powdered magnetic
particles 506 are contained in the gap surrounding
the disk 500. A coil of wire 508 is wound around
the cylindrical cavity 504.

When an electrical current travels through the
coil 508, a magnetic field parallel to the cylindrical
axis of the disk 500 is produced in the cavity 504.
The magnetic particles 506 in the gap align to form
what resemble 'chains' in response to the magnetic
field, and these chains of particles 506 resist the
motion of the disk 500 as it rotates along with the
output shaft 502 to which it is attached, thereby
retarding the rotation of the output shaft 502 about
the axis A and making the joint stiffer. The particle
brake has a resistive torque approximately propor-
tional to the current applied to coil 508. The brak-
ing strength may therefore be controlled by varying
the applied coil current.

Placid Industries B115P magnetic particle
brake is a suitable brake for B1, B2 and B3, while
model B15P may be used for brakes B4, B5, and
B6. Models B115P and B15P have rated torques of
13 and 1.7 N.m (115 and 15 inch-lbs), respectively,
at rated currents of 1/3 and 1/4 Amps, maximum
speeds of 1800 and 2000 r.p.m., and a de-en-
ergized drag of 0.176 and 3.5 x 10 -2 N.m (25 and
5 ounce-inches), respectively. The torque output of
the first three brakes may be amplified using re-
ducers, as described in the next section.

III. Reducers

Reducers 204 are used to amplify the torque
output of particle brakes B1, B2, and B3 by ap-
proximately four times using cable drive transmis-
sions. Figure 6 illustrates an exemplary reducer
transmission, i.e., the transmission for joint 300. A
capstan 600, made of aluminum and having a
diameter of about 20.3cm (8 inches), is attached to
link 338 (of Figure 3), and is coupled by a
3.175mm (1/8 inch) diameter nylon-covered aircraft
cable 602 to a smaller diameter capstan 604, which
has a diameter of 5.08cm (2 inches) and is at-
tached to the output shaft 606 of particle brake 1.
The base 608 of particle brake B1 is attached to
link 336 (also see Figure 3). The rotation of link 338
occurs about a rotation axis that coincides with the
axis of symmetry of large capstan 600, and is
retarded with a resistive torque that is four times
that produced by the particle brake, per se. A

position sensor, described in more detail in Section
IV, consisting of a potentiometer 614 with a rotat-
able tuning arm 610 is coupled by pulley 612 to
capstan 606. Rotation of the output shaft 606 rela-

5 tive to the base 608 corresponds to a rotation of
link 338 relative to link 336. The potentiometer
tuning arm 610 of the position sensor therefore
indicates the amount that joint 300 (see Figure 3
between links 338 and 336) has been rotated.

w Figure 7 illustrates the more complicated cable

drive transmissions that couple brakes B2 and B3
to the linkage. As seen in Figure 7, joint 308 of
Figure 3 in fact consists of two joints, correspond-
ing to the intersection of links 338 and 342 and the

is intersection of links 342 and 344 of Figure 3.

Link 338 is attached to an 20.3cm (8 inch)
capstan 700, coupled by nylon-covered aircraft ca-
ble 702 to 2 inch capstan 704 which is attached to
the base 706 of a particle brake B2. The output

20 shaft 708 of particle brake B2 is attached to a 2
inch capstan 710, which is coupled by aircraft
cable 712 to an 8 inch capstan 714 that is attached
to link 342 of Figure 3 (not shown in Figure 7).
Hence relative motion between the output shaft 708

25 and base 706 of particle brake B2 corresponds to
relative motion between links 338 and 342 via the 2
inch capstans 704, 710 and 20.3cm (8 inch) cap-
stans 700, 714, with links 338 and 342 rotating
about a rotation axis labelled 716 in the figure.

30 Conversely, resistive torque produced by particle
brake B2 is amplified via capstan pairs 704, 700
and 710, 714 to provide greater damping in the
relative motion between links 338 and 342.

Link 344 is attached to the base 718 of particle

35 brake B3. The output shaft 708 of particle brake
B3, which coincides with the output shaft of particle
brake B2, is likewise attached to 5.08cm (2 inch)
capstan 710, which is in turn coupled via aircraft
cable 712 to the 20.3cm (8 inch) capstan 714

40 attached to link 342 of Figure 3 (not shown in
Figure 7). Consequently, relative motion between
the output shaft 708 and base 718 of particle brake
B3 corresponds to relative motion between links
342 and 344 via the 2 inch capstan 710 and

45 20.3cm (8 inch) capstan 714, with links 342 and
344 rotating about rotation axis 716. Thus, resistive
torque produced by particle brake B3 is amplified
via capstan pair 710, 714 to provide greater damp-
ing in the relative motion between links 342 and

50 344.

IV. Position/Velocity Sensors

The six position/velocity sensors S1-S6, locat-
55 ed near and coupled to the manipulator linkage
joints 300, 308, 308, 304, 320 and 306 of Figure 3,
provide information as to the amounts that these
joints have been rotated (i.e., position information)

EP 0 569 489 B1

and how fast they are rotating (velocity informa-
tion). The position/velocity sensors at the joints
listed above correspond to the DOF's associated
with joints 300, 308, 402, 404, 406 and 306 of
Figure 4, respectively, and are hereafter referred to
as position/velocity sensors S1-S6, for conve-
nience. Equivalently, position sensors S1-S6 in-
dicate the angle between the following pairs of
links: 336 and 338, 338 and 342, 338 and 344, 348
and 350, 350 and 360, and 358 and 372. The
velocity sensors indicate the rate of change of
these angles.

Referring back to Figure 6, a position sensor
consists of a 5KQ potentiometer 614 (such as the
Helipot model 6186-R5K L1.0 B604M potentiom-
eter) having a tuning arm 610 coupled to the output
shaft 606 of the joint by means of a pulley, so that
the rotation of the output shaft 606 causes the
tuning arm 610 of the potentiometer to rotate. This
rotational action varies the resistance of the poten-
tiometer as measured across two of its leads 616.
The value of the resistance R P indicates the
amount that the joint has been rotated. The resis-
tance value is determined by connecting the poten-
tiometer leads 616 to a voltage divider circuit com-
prising a voltage source E coupled in series with a
standard resistor R and the potentiometer value R P
(as shown in Figure 8) and measuring the voltage e
= E Rp/(R + R p ).

A velocity measurement is obtained by dif-
ferentiating the measurement provided by the posi-
tion sensor, using a well-known analog differentiator
circuit. Joints other than the six joints mentioned,
do not contribute to additional DOF's, therefore,
additional potentiometers at these joints would pro-
vide no additional position and/or velocity informa-
tion.

V. Force-Torque Sensor

Referring back to Figure 3, the force-torque
sensor (FTS) 374 is located at the manipulator
endpoint E to measure the load applied by the limb
coupling cuff 376 on the manipulator endpoint in
each of the six DOF's. That is, three forces and
three torques are measured. As will be shown in
detail in connection with Figs. 10-12, this measure-
ment process consists of several distinct steps.
First, a sensing element senses the deformation of
an elastic element 1000 in response to an applied
load. An electrical circuit (Figure 12) converts the
output of the sensing element into an electrical
signal suitable for computer interfacing. Finally, a
transformation is performed whereby the vector of
electrical measurements is mapped to a vector
whose elements are the applied forces and tor-
ques.

Shown in Figures 10a and 10b is the elastic
element 1000 machined from 7075-T6 aluminum
alloy. The elastic element, has an overall diameter
of 10.16cm (4 inches) and an overall thickness of

5 2.03cm (0.8 inches). The element consists of four
concentric annuli 1002-1008 having different thic-
knesses, and four spokes 1010 each being spaced
at 90 degree intervals radiating outward from the
center of the innermost annulus 1008. A number of

10 holes 1012, 1014 are drilled into the elastic ele-
ment. Holes 1012 and holes 1014 accommodate
screws securing a FTS cover plate and a limb
coupling cuff (not shown), respectively to the ele-
ment 1000. Hole 1016 accommodates the output

15 shaft of particle brake B6 (i.e., the brake coupled to
joint 306).

Strain gauges 1018 attached to each of the
spokes of the elastic element sense deformations
of the element. Two groups (a vertical group and a

20 horizontal group) of four strain gauges are attached
to each spoke. In each group, each of the four
gauges is attached to a different edge of the spoke
(which has a square cross-section).

In addition to sensing deformations, the strain

25 gauges also provide an electrical representation of
the deformation. Specifically, each strain gauge has
a nominal resistance of 120 Q which varies with the
sensed strain. Referring to Figure 11, four strain
gauges (a.k.a. variable resistors) 1100-1106, two

30 from each group on a particular spoke, are elec-
trically configured to form a Wheatstone bridge
circuit (see Figure 12). The voltage vi across the
bridge is measured. A nonzero value of vi in-
dicates unequal strain gauge resistance values.

35 The remaining four strain gauges on the spoke
1108-1114 (again, two from each group) also pro-
vide a voltage, v 2 , in a similar manner. The two
measured voltages vi and V2 provide information
as to the horizontal and vertical components of the

40 applied force, respectively. The strain gauges on
the other three spokes provide this voltage informa-
tion in the same way, therefore, a vector of vol-
tages v = [vi v 2 ... vg] T is obtained.

Finally, voltage vector v is converted to a force

45 vector f via the transformation

f = Cv,

where the first three elements of f are the mea-
50 sured values of the three orthogonal components of
the applied force and the last three elements are
the values of the components of the applied torque,
and C is a 6X8 matrix whose elements were ob-
tained through calibration using applied forces and
55 torques of known magnitude.

EP 0 569 489 B1

VI. Limb Coupling Cuff

Applications

In a general sense, the manipulator of the
invention is a system for controllably resisting the
movement of a limb. Accordingly, the manipulator
can be used in a number of different applications.

One such application is that in which the ma-
nipulator is used as an exercise machine. The
microcomputer 104 of Figure 1 is programmed to

display a moving target 1300 on the display moni-
tor 108, as shown in Figure 9. Simultaneously, the
subject 102 attempts to pursue the target 1300 by
moving his/her arm, as indicated by a crosshair
1302 displayed on the monitor 108. The motion of
the target can be programmed to correspond to
certain arm movements, so that certain muscles
can be exercised. Moreover, the amount of resist-
ing force can be controlled by varying coil currents
in the particle brakes so as to vary resistance
levels in the exercise machine.

Another application of the manipulator is in
physical therapy. Here, the manipulator would be
used in conjunction with a microcomputer and dis-
play monitor as above, with the goal being the
rehabilitation of certain muscles. Of course, in each
of these applications, the use of the display moni-
tor for pursuit tracking tasks is not necessary. The
manipulator could be used in the manner that con-
ventional weight-training and exercise machines are
used.

Claims

1. A system for resisting limb movement com-
prising

a) a plurality of links (338-366) joined by
joints (300-334) to form a linkage system
(200) between a fixed point in space and a
movable end point (370) of said linkage
system;

b) a limb coupler (376) for coupling a limb
to said end point (370);

c) a plurality of brakes (B1-B6) for resisting
translational link movement in at least three
mutually orthogonal directions and for re-
sisting rotational link movement about at
least three mutually orthogonal axes;

d) a plurality of position and velocity sen-
sors (S1-S6) for sensing the degree and
rate of translational and rotational movement
of said links (338-366) about said joints
(300-334) in the three directions and three
axes; and

e) a computer (106) coupled to said plurality
of position and velocity sensors (S1-S6)
wherein the sensed positions and rates gen-
erate signals which are coupled to at least
one brake to vary the amount of resistance

50 generated by the brake.

2. The system of Claim 1, wherein the linkage
system (200) moves in the direction of a force
applied to said end point (370).

3. A system of Claim 1 wherein the brake effects
a resistance in a direction opposite to the
endpoint velocity direction.

A limb coupling cuff, labelled 376 in Figure 3,
acts as the physical interface between the human
limb (in the present application, the arm) and the 5
manipulator, and has the function of transferring
loads from the manipulator to the limb. Preferably,
cuff 376 is made of plastic or plaster or styrofoam
and molded to the shape of the limb. The goal of
the cuff is to provide the stiffest, most solid con- w
nection between the manipulator and the limb, so
that manipulator control over the limb is maxi-
mized, without substantially sacrificing user com-
fort. A handle which is gripped by the user can be
used in place of the limb coupling cuff. 15

VII. Counterbalances

The load of the linkage structure described in
Section I with the equipment of Sections II— VI, is 20
unbalanced about the rotational axes of several
joints. For example, in Figure 3, the moment pro-
duced by the portion of the linkage (as equipped
with particle brakes, reducers, position sensors,
and the force-torque sensor) to the right of joint 25
314 exceeds the moment produced by the portion
to the left, giving the manipulator arm the tendency
to tilt downward on the right side. This effect
causes the human subject to feel a weight load at
the manipulator endpoint. At joint 308, a similar 30
imbalance exists. Finally, the two upper parallel-
ograms of the upper linkage do not balance the
lower parallelogram about joint 304.

To balance the load about each of these rota-
tional axes, counterbalance weights are placed at 35
appropriate locations in the manipulator structure.
First, certain particle brakes themselves act as
counterbalances. Particle brakes B2 and B3 act as
counterbalances for the rotational axis of joint 308,
brakes B4 and B5 act as counterbalances for the 40
rotational axis of joint 314, and brake B5 acts as a
counterbalance for the rotational axis of joint 304.
In addition, lead weights used solely for the pur-
pose of counterbalancing supplement the particle
brakes. Lead weights 378 and 380 attached to links 45
340 and 364 act to counterbalance loads about the
rotational axes of joints 308 and joints 314 and 304,
respectively.

EP 0 569 489 B1

4. A system of Claim 1 wherein the linkage sys-
tem further comprise at least three parallel-
ograms (P1-P3) of links and joints.

5. A system of Claim 1 wherein the brake further
comprises a first cylinder (504) with a first
diameter coupled to the brake, a second cyl-
inder (506) with a second diameter which is
wider than said first diameter coupled to a
rotating joint of the linkage system and a cable
(508) with one end connected to the second
cylinder (506), said cable is wrapped around
the first cylinder (504) to amplify the brake
torque.

6. A system of Claim 5 wherein the brake further
includes a position sensor (204), said sensor is
connected to the end of the cable opposite to
the end connected to the second cylinder.

7. A system of Claim 6 wherein at least one
brake is positioned on a linkage as a coun-
terbalance weight.

8. A system for resisting limb movement com-
prising

a plurality of links (338-366) joined by
joints (300-334) to form a linkage system (200)
including at least three parallelograms (P1-P3)
of links and joints between a fixed point in
space and a moveable end point (370) of said
linkage system;

a limb coupler (376) for coupling a limb to
said end point (370);

a plurality of brakes (B1-B6) for resisting
translational link movement in at least three
mutually orthogonal directions and for resisting
rotational link movement about three mutually
orthogonal axes;

a plurality of position sensors (S1-S6) for
sensing the degree of translational and rota-
tional movement about said joints in the three
directions and three axes;

a plurality of velocity (S1-S6) sensors for
sensing the rate of said translational and rota-
tional movement;

a first cylinder (504) with a first diameter
coupled to the brake;

a second cylinder (506) with a second
diameter which is wider than said first diameter
coupled to a rotating joint of the linkage sys-
tem;

a cable (508) with one end connected to
the second cylinder (506), said cable is
wrapped around the first cylinder (504) to am-
plify the brake torque;

and

a computer (106) wherein the sensed posi-

tions and rates generate signals which are
coupled to at least one brake to vary the
amount of resistance generated by the brake.

5 9. A method of exercising by resisting limb
movement not being for physical therapy com-
prising the steps of:

a) coupling a limb to a movable end point
(370) of a linkage system (200), said linkage

10 system including a plurality of links (338-

366) joined by joints to form a linkage sys-
tem between a fixed point in space and said
movable end point of said linkage system;

b) sensing the degree of translation and
15 rotation of said links (338-366);

c) sensing the rate of translation and rota-
tion of said links (338-366);

d) resisting translational link movements in
at least three mutually orthogonal directions;

20 e) resisting rotational link movements about

three mutually orthogonal axes; and
f) varying the translational resistances and
the rotational resistances in accordance with
the sensed positions and rates of movement

25 of the links.

10. A method as recited in Claim 9 wherein the
resistance is effected in a direction opposite to
the end point velocity direction; or

30 wherein the linkage system (200) further

comprises at least three parallelograms (PI-
PS) of links and joints; or

wherein the brake further comprises a first
cylinder (504) with a first diameter coupled to

35 the brake, a second cylinder (506) with a sec-

ond diameter which is wider than said first
diameter coupled to a rotating joint of the
linkage system (200) and a cable (508) with
one end connected to the second cylinder,

40 said cable is wrapped around the first cylinder

to amplify the brake torque.

Patentanspruche

45 1. Eine Anordnung zum Widerstandleisten gegen
GliedmaGenbewegungen, umfassend

a) eine Vielzahl von Verbindungsgliedern
(338-366), die durch Gelenke (300-334) ver-
bunden sind, um ein Gestangesystem (200)

50 zwischen einem festen Punkt im Raum und

einem beweglichen Endpunkt (370) des Ge-
stangesystems zu bilden;

b) einen GliedmaBenkoppler (376) zum Kop-
peln eines Gliedes an den Endpunkt (370);

55 c) eine Vielzahl von Bremsen (B1-B6) zum

Widerstehen einer Translations-Verbin-
dungsgliedbewegung in wenigstens drei zu-
einander orthogonalen Richtungen und zum

EP 0 569 489 B1

Widerstehen der Rotations-Verbindungs-
gliedbewegung um wenigstens drei zuein-
ander orthogonalen Achsen;

d) eine Vielzahl von Positions- und Ge-
schwindigkeitssensoren (S1-S6) zum Erfas-
sen des Grades und der Rate von Transla-
tions- und Rotations-Bewegung der Verbin-
dungsglieder (338-366) um die Gelenke
(300-334) in den drei Richtungen und drei
Achsen und

e) einen Computer (106), der an die Vielzahl
von Positions- und Geschwindigkeitssenso-
ren (S1-S6) gekoppelt ist, in dem die erfaB-
ten Stellungen und Raten Signale erzeugen,
die an wenigstens eine Bremse gekoppelt-
werden, um den Betrag des durch die
Bremse erzeugten Widerstandes zu variie-
ren.

2. Die Anordnung nach Anspruch 1 , bei der sich
das Gestangesystem (200) in der Richtung ei-
ner Kraft bewegt, die auf den Endpunkt (370)
angewendet wird.

3. Eine Anordnung nach Anspruch 1, bei der die
Bremse einen Widerstand in einer Richtung
bewirkt, die zu der Richtung der Endpunkt-
Geschwindigkeit entgegengesetzt ist.

4. Eine Anordnung nach Anspruch 1, bei der das
Gestangesystem weiterhin wenigstens drei Pa-
rallelogramme (P1-P3) aus Verbindungsglie-
dern und Gelenken umfaBt.

5. Eine Anordnung nach Anspruch 1, bei der die
Bremse weiterhin einen ersten Zylinder (504)
mit einem ersten Durchmesser, der an die
Bremse gekoppelt ist, einen zweiten Zylinder
(506) mit einem zweiten Durchmesser, der
breiter als der erste Durchmesser ist, welcher
an ein Drehgelenk des Gestangesystems ge-
koppelt ist, und ein Kabel (508), von dem ein
Ende mit dem zweiten Zylinder (506) verbun-
den ist, umfaBt, wobei das Kabel um den er-
sten Zylinder (504) gewickelt ist, um das
Bremsdrehmoment zu verstarken.

6. Eine Anordnung nach Anspruch 5, bei der die
Bremse weiterhin einen Positionssensor (204)
umfaBt, wobei der Sensor mit dem Ende des
Kabels verbunden ist, das dem Ende entge-
gengesetzt ist, das mit dem zweiten Zylinder
verbunden ist.

7. Eine Anordnung nach Anspruch 6, bei der we-
nigstens eine Bremse auf einem Gestange als
ein Gegengewicht positioniert ist.

8. Eine Anordnung zum Widerstandleisten gegen
GliedmaBenbewegungen, umfassend:

eine Vielzahl von Verbindungsgliedern (338-
366), die durch Gelenke (300-334) verbunden

5 sind, um ein Gestangesystem (200) zu bilden,

das wenigstens drei Parallelogramme (P1-P3)
von Verbindungsgliedern und Gelenken zwi-
schen einem festen Punkt im Raum und einem
beweglichen Endpunkt (370) des Gestangesy-

w stems einschlieBt;

einen GliedmaBenkoppler (376) zum Koppeln
eines Gliedes an den besagten Endpunkt
(370);

eine Vielzahl von Bremsen (B1-B6) zum Wi-

15 derstandleisten gegen Translations-Verbin-

dungsgliedbewegung in wenigstens drei zuein-
ander orthogonalen Richtungen und zum Wi-
derstandleisten gegen Rotations-Verbindungs-
gliedbewegung um drei zueinander orthogona-

20 le Achsen;

eine Vielzahl von Positionssensoren (S1-S6)
zum Erfassen des Grades der Translations-
und Rotationsbewegung um die besagten Ge-
lenke in den drei Richtungen und den drei

25 Achsen;

eine Vielzahl von Geschwindigkeitssensoren
(S1-S6) zum Erfassen der Rate der Transla-
tions- und Rotationsbewegung;
einen ersten Zylinder (504) mit einem ersten

30 Durchmesser, der an die Bremse gekoppelt ist;

einen zweiten Zylinder (506) mit einem zweiten
Durchmesser, der groBer als der besagte erste
Durchmesser ist, welcher an ein Drehgelenk
des Gestangesystems gekoppelt ist;

35 ein Kabel (508), von dem ein Ende mit dem

zweiten Zylinder (506) verbunden ist, wobei
das Kabel um den ersten Zylinder (504) gewik-
kelt ist, um das Bremsdrehmoment zu verstar-
ken; und

40 einen Computer (106), in dem die erfaBten

Positionen und Raten Signale erzeugen, die an
wenigstens eine Bremse gekoppelt werden,
um den Betrag des durch die Bremse erzeug-
ten Widerstands zu variieren.

9. Ein Verfahren zum Oben durch Widerstandlei-
sten gegen GliedmaBenbewegung, jedoch
nicht fur physikalische Therapie, das die
Schritte umfaBt:

50 a) daB ein Glied an einen beweglichen End-

punkt (370) eines Gestangesystems (200)
gekoppelt wird, wobei das Gestangesystem
eine Vielzahl von Verbindungsgliedern (338-
366) umfaBt, die durch Gelenke miteinander

55 verbunden sind, um ein Gestangesystem

zwischen einem festen Punkt im Raum und
dem beweglichen Endpunkt des Gestange-
systems zu bilden;

EP 0 569 489 B1

b) der Grad der Translation und der Rota-
tion der Verbindungsglieder (338-366) erfaGt
wird;

c) die Rate der Translation und der Rota-
tions der Verbindungsglieder (338-366) er- 5
fafit wird;

d) Widerstand gegen Translations-Verbin-
dungsgliedbewegungen in wenigstens drei
zueinander orthogonalen Richtungen gelei-

stet wird; 10

e) Widerstand gegen Rotations- Verbin-
dungsgliedbewegungen urn drei zueinander
orthogonale Achsen geleistet wird; und

f) die Translationswiderstande und die Rota-
tionswiderstande in Ubereinstimmung mit 15
den erfaBten Positionen und Raten der Be-
wegung der Verbindungsglieder variiert wer-
den.

d) plusieurs capteurs de vitesse et de posi-
tion (S1-S6) pour detecter I'amplitude et le
rythme de mouvement en rotation et en
translation desdits organes de liaison (338-
366) autour desdits joints (300-334) dans
les trois directions et les trois axes, et

e) un calculateur (106) couple auxdits plu-
sieurs capteurs de vitesse et de position
(S1-S6), dans lequel lesdites positions et
rythmes captes engendrent des signaux qui
sont couples a au moins un frein pour faire
varier la valeur de resistance engendree par
le frein.

2. Systeme selon la revendication 1, dans lequel
le systeme de liaison (200) se deplace dans le
sens d'une force appliquee audit point d'extre-
mite (370).

10. Ein Verfahren nach Anspruch 9, bei dem der
Widerstand in einer Richtung bewirkt wird, die
der Richtung der Endpunktgeschwindigkeit
entgegengesetzt ist; oder
das Gestangesystem (200) weiterhin wenig-
stens drei Parallelogramme (P1-P3) aus Ver-
bindungsgliedern und Gelenken umfaGt; oder
bei dem die Bremse weiterhin einen ersten
Zylinder (504) mit einem ersten Durchmesser,
der an die Bremse gekoppelt ist, einen zweiten
Zylinder (506) mit einem zweiten Durchmes-
ser, der breiter als der erste Durchmesser ist,
welcher an ein Drehgelenk des Gestangesy-
stems (200) gekoppelt ist, und ein Kabel (508)
umfaBt, von dem ein Ende mit dem zweiten
Zylinder verbunden ist, wobei das Kabel um
den ersten Zylinder gewickelt ist, um das
Bremsdrehmoment zu verstarken.

Revendications

1. Systeme restreignant les mouvements d'un
membre comprenant :

a) plusieurs organes de liaison (338-366)
raccordes par des joints (300-334) pour for-
mer un systeme de liaison (200) entre un
point fixe dans I'espace et un point d'extre-
mite mobile (370) dudit systeme de liaison,

b) un dispositif de couplage de membre
(376) pour coupler un membre audit point
d'extremite (370),

c) plusieurs freins (B1-B6) pour restreindre
le mouvement d'organe de liaison en trans-
lation dans au moins trois directions per-
pendiculaires mutuellement et pour restrein-
dre le mouvement d'organe de liaison en
rotation autour d'au moins trois axes per-
pendiculaires mutuellement,

20 3. Systeme selon la revendication 1, dans lequel
le frein applique une resistance dans un sens
oppose au sens de vitesse du point d'extremi-
te.

25 4. Systeme selon la revendication 1, dans lequel
le systeme de liaison comprend en outre au
moins trois parallelogrammes (P1-P3) de joints
et d'organes de liaison.

30 5. Systeme selon la revendication 1, dans lequel
le frein comprend en outre un premier verin
(504) avec un premier diametre, couple au
frein, un second verin (506) avec un second
diametre, qui est plus grand que ledit premier

35 diametre, couple a un joint rotatif du systeme

de liaison et un cable (508) avec une extremite
connectee au second verin (506), ledit cable
etant enroule autour du premier verin (504)
pour amplifier le couple de freinage.

6. Systeme selon la revendication 5, dans lequel
le frein comprend en outre un capteur de posi-
tion (204), ledit capteur etant connecte a i'ex-
tremite du cable opposee a I'extremite

45 connectee au second verin.

7. Systeme selon la revendication 6, dans lequel
au moins un frein est place sur une liaison en
tant que poids d'equilibrage.

8. Systeme restreignant les mouvements d'un
membre comprenant :

- plusieurs organes de liaison (338-366)
raccordes par des joints (300-334) pour
55 former un systeme de liaison (200), com-

prenant au moins trois parallelogrammes
(P1-P3) de joints et d'organes de liaison
entre un point fixe dans I'espace et un

EP 0 569 489 B1

point d'extremite mobile (370) dudit sys-
teme de liaison,

un dispositif de couplage de membre
(376) pour coupler un membre audit
point d'extremite (370), 5
plusieurs freins (B1-B6) pour restreindre
le mouvement d'organe de liaison en
translation dans au moins trois directions
perpendiculaires mutueilement et pour
restreindre le mouvement d'organe de w
liaison en rotation autour de trois axes
perpendiculaires mutueilement,
plusieurs capteurs de position (S1-S6)
pour detecter I'amplitude du mouvement
en rotation et en translation autour des- 15
dits joints dans les trois directions et les
trois axes,

plusieurs capteurs de vitesse (S1-S6)
pour detecter le rythme dudit mouve-
ment en rotation et en translation, 20
un premier verin (504) avec un premier
diametre couple au frein,
un second verin (506) avec un second
diametre, qui est plus grand que iedit
premier diametre, couple a un joint rotatif 25
du systeme de liaison,
un cable (508) avec une extremite
connectee au second verin (506), iedit
cable etant enroule autour dudit premier
verin (504) pour amplifier ie couple de 30
freinage, et

un calculateur (106) dans lequel les ryth-
mes et positions captes engendrent des
signaux qui sont couples a au moins un
frein pour faire varier la valeur de resis- 35
tance engendree par le frein.

e) restreindre des mouvements d'organe de
liaison en rotation autour de trois axes per-
pendiculaires mutueilement, et

f) faire varier les resistances en translation
et les resistances en rotation selon les ryth-
mes et positions captes de mouvement des
organes de liaison.

10. Procede selon la revendication 9, dans lequel
la restriction est appliquee dans un sens oppo-
se au sens de vitesse du point d'extremite, ou
dans lequel le systeme de liaison (200) com-
prend en outre au moins trois parallelogram-
mes (P1-P3) d'organes de liaison et de joints,
ou dans lequel le frein comprend en outre un
premier verin (504) avec un premier diametre,
couple au frein, un second verin (506) avec un
second diametre, qui est plus grand que Iedit
premier diametre, couple a un joint rotatif du
systeme de liaison (200) et un cable (508)
avec une extremite connectee au second verin,
Iedit cable etant enroule autour du premier
verin pour amplifier le couple de freinage.

9. Procede d'entraTnement en restreignant le
mouvement d'un membre, non destine a une
therapie physique, comprenant les etapes de : 40

a) couplage d'un membre a un point d'ex-
tremite mobile (370) d'un systeme de liai-
son (200), Iedit systeme de liaison compre-
nant plusieurs organes de liaison (338-366)
relies par des joints pour former un systeme 45
de liaison entre un point fixe dans I'espace

et Iedit point d'extremite mobile dudit syste-
me de liaison,

b) detecter I'amplitude de la translation et

de la rotation desdits organes de liaison 50
(338-366),

c) capter le rythme de translation et de
rotation desdits organes de liaison (338-
366),

d) restreindre des mouvements d'organe de 55
liaison en translation dans au moins trois
directions perpendiculaires mutueilement,

EP 0 569 489 B1

I02

HUMAN SUBJECT

I00

MONITOR -I08

I06

I04

MANIPULATOR

I t

PREPROCESSING
ELECTRONICS

1 t

MICROCOMPUTER

102a

100

206

LIMB COUPLER
CUFF

212

POSITIONAL
VELOCITY
SENSORS

FORCE

TORQUE

SENSOR

7
208

204

REDUCERS

"I
I
I

210

202

BRAKES
~I

COUNTERBALANCES

PROCESSOR

106

EP 0 569 489 B1

202

508

JL.

204

EP 0 569 489 B1

344

7I6

— ^-TO LINE
342 FIG. 3

7I2

336

600

EP 0 569 489 B1

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